Antibiotic resistance poses a serious threat to global public health, and antibiotic resistance genes can enter natural aquatic systems through discharge of wastewater effluents. Hospital wastewater in particular is expected to contain high abundance of antibiotic resistance genes (ARGs) and can contain elevated concentrations of antibiotics and antimicrobials relative to municipal wastewater. Viruses also play an important role in wastewater treatment systems since they can influence the bacterial community composition through killing bacteria, facilitating transduction of genetic material between organisms, and modifying the chromosomal content of bacteria as prophages. However, little is known about the fate and connections between ARGs, viruses, and their associated bacteria in hospital wastewater treatment systems.<br/><br/>To address this knowledge gap, we characterized the composition and persistence of ARGs, double stranded DNA viruses, and bacteria from influent, biological treatment, and effluent in a pilot-scale hospital wastewater treatment system that includes anaerobic, anoxic, and aerobic secondary treatment processes in Israel using shotgun metagenomics. Results showed that ARGs, including genes conferring resistance to antibiotics of high clinical relevance, were detected in all sampling locations throughout the pilot-scale system, with only 16% overall depletion of ARGs per genome equivalent between influent and effluent. The most common classes of ARGs detected throughout the system conferred resistance to aminoglycoside, cephalosporin, macrolide, penam, and tetracycline antibiotics. Results indicate that a high proportion of ARGs were likely associated with horizontal gene transfer in all samples with a possible but small enrichment in the effluent compared to in the influent. No strong associations between viral sequences and ARGs were identified in viral metagenomes from the system, suggesting that phage may not be a significant vector for ARG transfer in this system. Overall, we found that a variety of different types of ARGs and viruses were persistent throughout this hospital wastewater treatment system, which can be released to the environment through effluent discharge.

Antibiotic resistance of microbial and viral communities in a hospital wastewater treatment system

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ACS Fall 2022

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